(1) Field of the Invention
The present invention relates to a reflecting mirror for guiding image light expansion-projected by a projector lens to the back face of a screen, and to a projection type image display apparatus using the reflecting mirror.
(2) Description of the Related Art
A projection type image display apparatus utilizes a reflecting mirror for the downsizing of the set; the reflecting mirror involves reflecting image light from an image generating source such as a CRT, or a liquid crystal panel for changing the light path, and then guiding the image light to the back face of a transmission screen. The metal reflection film (metal reflection layer) of the reflecting mirror conventionally uses aluminum (Al); however, a metal reflection film is also proposed which employs silver (Ag) having little dependency of the reflection factor on the wavelength, as will be shown in the following three patent documents.
Japanese Patent Laid-open No. 2003-255467 below discloses formation of a silver reflection film on a glass substrate using a spray apparatus by silver mirror reaction. Japanese Patent Laid-open Nos. 9-189803 and 9-311207 disclose formation of a silver thin film on a substrate made of resin such as acrylic by vapor deposition.